Very simple moving platform script does not work?

So, today I decided to type this script for a simple moving platform for my running game.

But, somehow it is saying that BodyPosition is not a valid member of BodyPosition. I'm in need of help I've tried to fix it but it still come up with BodyPosition is not a valid member of BodyPosition. I_('-')_I

local start = game.Workspace.Start
local finish = game.Workspace.Finish
local localpart = script.Parent
while true do 
wait(1.5)
localpart.BodyPosition.Position = finish.Position
wait(1.5)
localpart.BodyPosition.Position = start.Position
end
--// no idea why its not working

Hmm, maybe I need to access the start and position in a different way so I create a model so I can use the model to get to the Start and Position, If that makes sense.

local localpart =  script.Parent
local start = script.Parent.Parent.Parent:FindFirstChild("Start")
local finish = script.Parent.Parent.Parent:FindFirstChild("Finish")
while true do
wait(1.5)
localpart.BodyPosition.Position = finish.Position
wait(1.5)
localpart.BodyPosition.Position = start.Position
end

Wow, still doesn't work still goes to a position I don't want it to be at... And guess what I still get the same Output...

I need help for this very simple script. lol